She had just been released from hospital when she suffered severe shortness of breath at home and suffered a heart attack in the ambulance leading to her death last year.

Belfast Coroner Joe McCrisken said: "It seems on the balance of probabilities it is likely there was some sort of leak from around the surgical site."

Mrs Sloan, a married retired domestic assistant from Fountain Lane in Antrim, died at Antrim Area Hospital on September 7 last year.

She had been suffering bouts of chest infection linked to a cancerous growth in her lungs amid an underlying respiratory problem and after extensive assessment doctors decided to operate to try to prevent a fatal pneumonia.

Surgeon Kieran McManus said: "She agreed to proceed to the surgery fully informed that she is a high risk case."

The operation went according to plan and there was no sign of an air leak over more than a week's recovery in hospital.

However shortly after she went home she became severely short of breath and was taken back to hospital in an ambulance.

She suffered a heart attack en route and was later pronounced brain dead by doctors.

Mr McManus said there could have been a number of reasons for the leaking of air from her lung including efforts to resuscitate her.